metal-free reductionsystem, in which H2Se (or HSe–) produced in situ from Se/DMF/H2O acts as the active reducing species, has been developed. By using water as an inexpensive, safe, and environmentally friendly surrogate as the hydrogen donor, this newreductionsystem incorporating Se/DMF/H2O displayed high selectivity and good activity in the reduction of α,β-unsaturated ketones and alkynes. Therefore
一种新型的无金属还原系统,其中H 2 SE(或HSE组- )原位产生从硒/ DMF / H 2 ö充当活性还原物质,已经研制成功。通过使用水作为廉价,安全和环保的替代物作为氢供体,这种结合了SE / DMF / H 2 O的新还原系统在还原α,β-不饱和酮和炔烃方面显示出高选择性和良好的活性。因此,该还原系统具有很大的潜力,可以作为有机转化中通用而实用的还原方法。
Reaction of diisobutylaluminium hydride with selenium and tellurium: new reagents for the synthesis of seleno- and telluro-amides
作者:Guang Ming Li、Ralph A. Zingaro
DOI:10.1039/a707792k
日期:——
Diisobutylaluminium hydride (Bui2AlH) undergoes reaction with elemental selenium and tellurium to afford new reagents having an Al–Se or an Al–Te bond. These directly convert amides to selenoamides and telluroformamides. This affords a one-pot route to selenoamides and telluroformamides starting from Se and Te, and may be suitable for large scale syntheses.
An efficient synthesis of selenoaldehydes, selenoketones, and selenoamides was achieved by the treatment of carbonyl compounds with bis[1,5-cyclooctanediylboryl] selenide.
Selenoaldehydes and selenoketones were generated in situ, by treating aldehydes or ketones, respectively, with bis(1,5-cyclooctanediylboryl) selenide; the resulting selenocarbonyl compounds were trapped with 2,3-dimethyl-1,3-butadiene to give the corresponding [4+2] cycloadducts. The treatment of amides, an ester, and ketones possessing bulky substituents with the reagent also afforded the corresponding selenoamides, a selenoester, and sterically protected selones, respectively, in modest yields. On the other hand, a similar treatment of cinnamaldehyde with the reagent gave the 2,3-dihydroselenophene derivative, which originated from a [4+2]-type self-dimerization of in situ generated 3-phenyl-2-propeneselenal.
Conversion of Amides,<i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-Tetramethylurea, and Esters to the Corresponding Selenoxo Compounds by Treatment with Bis(trimethylsilyl) Selenide and BF<sub>3</sub>·OEt<sub>2</sub>
The reactions of amides and N,N,N′,N′-tetramethylurea with (Me3Si)2Se in the presence of BF3·OEt2 afforded the corresponding slelenoxo compounds in good yields. On the other hand, selenation of ethyl and butyl benzoates in a similar manner gave benzoin and 2,3,5,6-tetraphenyl-1,4-diselenin via selenoesters. The trapping of selenoesters was also achieved by 2,3-dimethyl-1,3-butadiene to afford [4+2] cycloadducts.